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Activities that were developed for better/modern living conditions of humans are the primary source of contaminants to the natural ecosystem. Some of the compounds involved in urbanization and industrialization are termed emerging contaminants (ECs) or contaminants of emerging concern. ECs are either chemical or derived from natural sources which environmental concerns and public health have been raised in recent years. ECs enter wastewater treatment systems and migrate from here to different ecosystems as direct or by-products. They are persistent and also stay for a long duration due to their less biodegradation and photodegradation nature. Also, ECs accumulated in living cells and transformed through trophic levels. Technological developments and their application/utility in daily life led to the production of various components that are being added to the natural ecosystem. The treated/untreated wastewater enters into fresh/marine water bodies and gets accumulated into fauna, flora, and sediments. These pollutants/contaminants that are getting added on an everyday basis bring about changes in the existing ecosystem balances. ECs have been found in almost every country’s natural environment, and as a result, they became a global issue. The present review discusses the route and transport of selected ECs into the terrestrial ecosystem through water and other means and how they influence the natural process in an ecosystem. The ECs such as personal care products, pharmaceuticals, polyaromatic hydrocarbons, endocrine disruptors, nanoparticles, and microplastics are highlighted in this review.

To further facilitate commercialization of automotive fuel cells, durability concerns need to be addressed. Currently the addition of a mechanical support in the membrane is able to adequately solve issues of mechanical degradation, but chemical degradation via oxygenated radical attack remains an unsolved challenge. Typical mitigation strategies use cerium or manganese species to serve as radical scavengers, but these ions are able to migrate in the membrane and even leach out of the system. The approach used in this study is to covalently link and immobilize a heteropoly acid (HPA), more specifically 11-silicotungstic acid (HSiW11), a lacunary HPA of the Keggin structure to a fluoroelastomer, serving as both a radical decomposition catalyst and the proton conducting acid. This dual functionality allows for both high content of radical scavenging species and high ion-exchange capacity. An efficient three step, high yield (77%), commercially viable synthesis for this polymer is reported. The synthesis route for making this new heteropoly acid functionalized polymer is confirmed using infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis (TGA). The material exhibits clustering of the HSiW11 moieties, resulting in a poorly connected proton conducting phase when dry, but excellent conductivity is achieved at elevated humidities (0.298 S cm−1 at 80 °C and 95% RH). The proton conductivity shows an enhancement above 60 °C due to a softening of the polymer, as shown by DSC. Under an aggressive chemical accelerated stress test (AST), 90 °C, 30% RH, zero current, and pure O2, the PolyHPA losses only 0.05 V of open circuit voltage (OCV) after 500 h, greatly out performing any other material reported in the literature. For comparison, the Nafion® N211 fuel cell drops below 0.8 V after only 76 h under the same conditions. In fuel cell testing the PolyHPAs have outstanding chemical stability and also possess very low in situ high frequency resistance (HFR) leading to high performance (1.14 W cm−2 at 2 A cm−2), compared to 1.11 W cm−2 for the Nafion® N211 fuel cell at the same current. At 75 wt% HSiW11 loading, the fuel cell HFR showed a 22% decrease over N211.

Water vapor transport through the PEM is one of the key parameters that can help achieve high performance and low-cost fuel cell system. Ex-situ water vapor transport rate (WVTR) measurement is extremely difficult and expensive to measure. This transport depends on many parameters such as ionomer equivalent weight, ionomer type, thickness, reinforcement, and operating conditions. This work presents a simplified and an inexpensive set-up that consists of fuel cell test stand, cell hardware, and a humidity sensor to measure WVTR at PEMFCs operating conditions in order to characterize and compare water transport properties of PEMs. WVTR is found to increase with decrease in EW and decrease in thickness. WVTR shows dependence on flow rates at fixed water vapor activity and increases by almost 2 times at flow rate from 0.1 to 4 L/min. WVTR is strongly dependent on RH% and increases by 4-5 times at RH from 30 to 100%. Overall, a simple and inexpensive set-up is developed which is capable of producing water vapor transport behavior of widely different PEMs.

Chemical and mechanical durability of polymer electrolyte membrane (PEM) must be understood and improved for commercial success of PEMFCs vehicles. Chemical degradation of PEMs occurs under OCV conditions due to high gas crossover, high concentration of chemically weak groups, and low EW. These properties measured ex-situ have been related to develop a chemical stability factor (CSF) to predict in-situ chemical durability of PEMs. Mechanical degradation of PEMs occurs under dry-wet cycling due to low tensile strain, high swelling, low EW and high gas crossover. A mechanical stability factor (MSF) has been derived from ex-situ measured % Strain at Break, % Swelling, oxygen crossover rate, and EW to predict in-situ mechanical durability of PEMs. The relative trend predicted by CSF and MSF follows the relative trend in in-situ chemical and mechanical durability. These factors can be used to screen and select the most durable PEM for in-situ testing in order to save lengthy in-situ testing time, developmental cost and resources.

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